This section provides background information related to the present disclosure which is not necessarily prior art.
Fastener elements such as a screw, nut, bolt, nail, rivet, etc., hereinafter referred to as fasteners, are used to join components together in a myriad of applications. With conventional installation tools, a fastener will engage either a drive socket for fasteners with external driving geometry, such as a hex head bolt, or the fastener will engage a drive bit for fasteners with internal driving geometry, such as a slot, cruciform or internal hex bore. Fasteners easily disengage from these conventional tools and thus an installer may steady a fastener in some fashion during the first phase of initial install until the fastener is installed to a degree its position is sufficiently maintained by the workpiece receiving said fastener. When fastening components together, the installer may need to manipulate or position those components before or while applying a fastener. It is not uncommon to see fasteners loosely applied by hand without any drive tools, prior to using such tools, since the conventional drive tools do not hold a fastener firmly enough to allow the installer to perform such manipulation after loading the fastener into or onto an installation tool.
For both fasteners with internal and external drive geometry, a fastener is engaged with the drive device by axially positioning the fastener into or around the drive device, after which point it is held there with a limited amount of friction. Multiple devices have improved upon the original state of concerns and may restrain a fastener from disengagement under the force of gravity and modest kinematics from the operator positioning the tool with the fastener loaded for install. The currently known approaches have features or operational requirements which may hinder productivity during their use. The following paragraphs discuss categorical approaches of the most relevant known prior art.
A first method employs one or more magnets to impart an axial pull on the fastener, urging it towards the drive mechanism, which may be done by fixing a magnet inside of a drive bore, or for internal drive geometries, the bit itself could be magnetized or a magnetic collar could be disposed around a drive bit so as to contact the face of the fastener directly. Designs with a magnet disposed around a drive bit are depicted in U.S. Pat. Nos. 2,641,290 and 7,124,665 (and are commercially available under several brands as of May 2015 including the Hammerhead model HAIB06.) Magnetic drivers have been available for use with drill drivers and other power tools. The drivers are used for driving fasteners, e.g., nuts and screws having a polygonal-shaped, e.g., hex-shaped head. This magnet may interfere with or complicate the loading process by pulling the fastener against the driving tool in an undesired orientation and alignment. Also a magnet may attract metal debris which can interfere with the intended usage of such drive devices. U.S. Pat. No. 8,695,461 provides a fastener holding magnet which can be slid forward in the driving assembly for easier cleaning of the magnet in order to reduce the issues caused by attracting debris, however this modification also increases the difficulty and awkwardness of fastener loading. With this approach, the ability of the fastener retaining mechanism to resist forces normal to the fastener and tool axis, or moments about any axis other than the drive axis, is limited and there is limited ability to prevent disengagement from mechanical procession under such loads. The axial holding force of the magnet is also limited.
A second type of approach employs a drive bit for internal fastener drive geometry, which expands inside that fastener's drive geometry to create retention force. This arrangement could reduce the strength of the drive bit so it may be best used for starting a fastener or installing fasteners which require limited install torque, thus such a mechanism may not be suited for use with a powered driver. Further, these devices often require manual actuation, which may consume time and thus may limit productivity of a user. The fastener retaining means of this approach may be limited. U.S. Pat. Nos. 1,063,304, 4,078,593, and 6,681,662 disclose varying approaches to this general concept.
A third approach employs multiple holding members comprised of a leaf spring, with some geometry on the end of said leaf spring to apply force to the underside of the fastener head in a radially inward and axial direction, urging the fastener against the drive mechanism. The leaf spring elements themselves may be fragile due to their required flexible nature and thus may not be well suited for use with a power driver or high volume applications. These tools may only seek to restrain the screw from disengaging under the force of gravity and the kinematics of the operator positioning the tool with the fastener loaded for install. This approach will often have a limited ability to retain fasteners. Further, the leaf springs may require additional operator intervention during the loading sequence, possibly during the installation sequence depending on the application and the feature geometry. Examples of this approach are disclosed in U.S. Pat. Nos. 815,758, 2,519,811 and 2,762,409.
A fourth type of approach employs jaws which pinch around the fastener to assist with maintaining axial alignment, longitudinal position or both. This is similar to the third approach, however the fastener holders with this approach may be shaped differently and actuated in a variety of manners. While this design approach may allow more robust constructions than the leaf spring approach, it may also contain many of the same drawbacks. One example of this approach is depicted in U.S. Pat. No. 4,236,555. The amount of force that can be exerted by these retaining means may be limited, so undesirable angular misalignment of the fastener from the driving axis may occur in operation. In order to load this device, a fastener is dropped into a loading tube, 24 in the figures. If gravity causes the fastener to drop down into the loading tube and then travel into the main bore of the tool, such a tool may only be suited for installing fasteners in a largely vertical direction. U.S. Pat. No. 6,244,141 discloses another approach to this design where the retention members (“clamps”) 150 and 151 are urged radially inwards by an outer sleeve 160 in order for these members to engage against the bottom surface of the screw head and hold the screw against the drive bit (102). With this design, the fastener is first located properly relative to the sleeve and then the outer sleeve 160 may need to be manually positioned during the loading sequence. Since this tool is intended to be held in either a hand or power tool, either of which could be held in one of a user's hands during operation, in order to prevent a fastener from falling off the tool, it may need to be turned into a largely vertical, upside down fashion with the bit pointing up such that the fastener does not fall off the driving device when the user loads the screw with a second hand and then releases that screw to use the same second hand to position the sleeve 160. U.S. Pat. No. 6,539,826 discloses a device used for driving screws with specially formed heads in which jaws 3 and 4 have connected features 19, 20 for engaging with and transmitting torque to drive geometry 13 on the screw head. When a user loads a screw, they supply force to the screw to position components 30, 3, and 4 during which the frictional retention of those components must be overcome, including the position retaining force created by spring loaded pin 36 engaging groove 34. Jaws 3 and 4 are forced radially inward by means of a bore in holder 2 to capture a screw head. After full installation of the screw, the tool may then be pulled away from the screw, releasing it in the process. U.S. Pat. No. 3,901,298 discloses another similar approach in which a user may manually position a sleeve against the force of a spring to hold fastener retention jaws in an open position while loading a fastener. A user holding the driving tool, while also pushing sleeve 52 forward and loading a fastener, may be an awkward task. Further, the sleeve is pushed forward at some point in the installation sequence to release the jaws from the fastener to allow for complete installation without obstruction from the fastener retaining components. User intervention during loading and release of a fastener may limit productivity.
A fifth approach employs a plurality of radially traveling segments in a collet type arrangement that can be radially expanded or compressed through a variety of mechanical means. This may put pressure directly on a fastener to clamp it, or it may close around the fastener and geometrically prevent unintended removal by means of a relief slot in the fastener-engaging side of the movable segments. U.S. Pat. No. 6,497,166 discloses such an approach where a collet 40 includes prongs 24 with an internal groove 62 used to hold the head of a screw. The prongs 24 are such that they may surround a screw head 38 without grippingly engaging it until biased inwardly. To clamp the screw, an operator slides sleeve 22 forward, towards the screw being loaded. During installation, the sleeve 22 will contact a work surface and travel rearward, thereby opening the prongs 24 and releasing the screw. Thus a user of this tool may need to manually position the sleeve 22 after loading a fastener. To operate, a user may need to hold the driver, place a fastener, and then hold the fastener while sliding the sleeve 22 forward. This intervention may limit productivity. U.S. Pat. No. 2,658,538 describes a similar approach. In this arrangement, a user may need to manually retract the sleeve (“housing”) 44 in order to load a screw. In operation of this device, the screw is released from the device automatically based on item 50 contacting the work surface and retracting the sleeve 44 without additional intervention from the user. Manual intervention of the tool while loading may limit productivity.
A sixth approach is to have a sleeve slidably disposed about the shank of a driving tool, including a flange capping the end of said sleeve wherein said capping flange has a reduced cross-sectional opening which is too small to permit axial passage of a fastener. A fastener can be loaded into such a holder by passing laterally through a radial slot in the sleeve so that the head of the fastener can be urged against a driving bit or socket by force exerted by this capping flange, said force typically coming from a spring. After substantially installing the fastener into the workpiece, the sleeve may be slid slightly forward in order to allow clearance between the driving tool and the fastener head. The driving tool is then moved laterally past the fastener where the head of said fastener will pass through the aforementioned slot in the sleeve. The sleeve can then be freely retracted such that a driving bit can protrude sufficiently past the capping flange of the sleeve to complete full installation of the fastener. This approach is depicted in U.S. Pat. No. 2,796,100 where the head 14 has a slot 18 in the end and a capping flange 19 has a slot 20 to permit engaging and disengaging a fastener 9 with the driver 1. In this case the sleeve assembly 8 (“holding means”) is positioned longitudinally and held by use of a cam sleeve 30. Similar approaches which utilize varying mechanics and operational procedures can be seen in U.S. Pat. Nos. 2,774,401, 2,884,971, and 8,539,865. Screw-holding screwdrivers employing this approach, and utilizing a simple spring to continuously urge the retaining sleeve in a rearward direction, are commercially available under the Greenlee brand at the time of this application, such as item #0453-18C for driving #2 Phillips bits and other models for other head types. The approach of this category may be best suited for applications where the amount of time spent loading a fastener is of secondary importance. User intervention to load the fastener, as well as to disengage the driver part-way through the fastener installation, may make use with a power driver impractical and this manipulation may limit productivity.
A seventh approach provides a sleeve into which an entire fastener can be slid for rough guidance. This approach provides axial guidance, though possibly in a limited sense, as the full bore of the sleeve must be greater than the diameter of the head and the leading point of the fastener is often significantly smaller. It is thus possible for a fastener to be located within such a sleeve with angular misalignment from a drive bit or socket, such as having the fastener head roughly centered below the driving bit or socket and the fastener shank bearing against the inner wall of the sleeve near the distal end where the device makes contact with the work surface. Thus this approach may not be appropriate for fasteners which require precise axial alignment. Further, as coaxial misalignment between a fastener and mating bit or socket increases, the ability to transmit drive torque and prevent disengagement of the two may be limited. This general type of fastener driving device is depicted in U.S. Pat. No. 1,644,074 and products commercially available since at least 2003, for example, what is currently marketed at the time of this application under Dewalt part number DW2055, Bosch part number CC60491 and many others. In operation of the aforementioned commercially available driving devices, the retaining sleeve may need to be re-positioned between each fastener installation, pulling the outer sleeve forward since it is pushed rearward whenever a fastener is installed. This user intervention may limit productivity. U.S. Pat. No. 6,668,941 proposes an improvement to this device wherein the outer sleeve is spring-loaded to automatically return its forward-most position without additional user intervention, thus theoretically reducing time to manually position the sleeve.
An eighth approach utilizes a plurality of drive sections stacked axially upon each other, which can have a torsional force applied between them for purpose of retaining a fastener by various types of drive geometry. U.S. Pat. No. 8,020,472 discloses one such device (“nut capturing socket assembly”) 20, which utilizes a sleeve 24 with generally the same drive geometry as a main drive socket 22, but is torsionally disposed about that main drive socket. A user may need to rotate this sleeve 24 to align the drive geometry with that of socket 22, at which point a fastener may be loaded. The operator may release the device after loading the fastener and the relative torsion between the socket 22 and the sleeve 24 will create friction on the outer surface of the fastener to resist dropping of the fastener. The process of manipulating the driving device 20 while loading the fastener may be somewhat awkward with a user holding either the socket 22 or the shank that will provide driving rotation to this device, while also rotating sleeve 24 and loading a fastener. Further, the amount of retaining force possible may be directly related to the torque applied by the torsion creating means which, for purpose of tolerable user actuation, may be relatively small. Holding force applied to the fastener could thus be limited in this approach. Manipulation of the tool may limit productivity.
A ninth approach uses a resilient member such as a spring to urge retaining elements radially inward to capture the underside of a fastener head. This may be done by having a resilient member pushing directly on retaining elements, such as in U.S. Pat. No. 2,235,235, or it may be done indirectly by a spring urging a cam sleeve, which in turn urges retaining elements radially inward, such as in U.S. Pat. No. 5,996,452. It should be noted in each of these patents, the spring force which urges the retaining elements radially inward may need to be overcome by a user when loading a fastener. A correlation may exist between the force available to retain a fastener against external forces and the force required to overcome the resilient force urging the retaining elements radially inward when loading a fastener. The time spent loading such a device and the screw retention capacity of this approach may limit productivity.
A tenth approach, somewhat similar to the ninth approach, is designed such that a cam sleeve will pass the retaining elements in such a manner that the resilient member (usually a spring) is used merely to position the sleeve, not to directly or indirectly provide the holding force. In this fashion, once the components are positioned, something else must reposition them to allow the retaining elements to release the fastener. During installation that allows very high forces to be exerted by the retaining elements, and thus the driving tool may resist a high level of axial force, and prevent disengagement due to force perpendicular to the fastener axis and moment forces between the driver and the fastener. U.S. Pat. No. 5,341,708 details once such embodiment of this approach. In this patent, a body 41 is locked upon a drive bit 21. A body member 71 is urged forward relative to body 41 by a spring 60. Member 71 has multiple apertures 93 located at the forward end in which a plurality of ball bearing retaining jaws 111 are carried. A cam sleeve 131 is biased forward relative to body member 71 by a second spring 90. Cam sleeve 131 has a pair of bores, 141 which is slightly larger than the diameter of body 71 and bore 142 which is a larger diameter and located at the forward end of sleeve 131.
When bore 142 is substantially aligned with retaining jaws 111, they can be retracted in the apertures 93 so as not to restrict the loading and unloading of a fastener 30. However, when sleeve 131 is in its forward position, the smaller bore 141 will be substantially aligned with apertures 93, thus forcing the retaining jaws 111 radially inward towards the tool's central axis, whereby passage of a screw head past the balls to load or unload a screw is prevented.
When no screw is loaded, body 71 and sleeve 131 will be at their forward-most position with retaining jaws 111 protruding into the bore of body 71, thus preventing a screw from being loaded until sleeve 131 is pulled rearward by a user. At that point, a screw 30 can be positioned on bit 21 and sleeve 131 can be released. Sleeve 131 will travel forward, thereby pushing retaining jaws 111 into the central bore of body 71, obstructing said bore enough to prevent removal of the screw.
Since the bore 142 passes the center of retaining jaws 111, outward force on the retaining jaws created by any attempt to remove the screw may not cause sleeve 131 to move rearward, thus the screw is mechanically locked in the loaded position. This feature distinguishes devices of this category from the prior ninth category presented. As a screw is being installed, sleeve 131 will contact a work surface and it will be retracted to release the screw to allow for full fastener installation without manual manipulation after driving has begun. A user manipulating sleeve 131 in order to load a screw may be an awkward task considering the user may need to concurrently hold or steady the driving tool such as a drill, retract sleeve 131 and load the screw. The time spent for this manipulation, while loading, may limit productivity.
U.S. Pat. Nos. 4,140,161 and 5,207,127 and US Patent application 20020166421 utilize similar mechanical components, which require direct manual manipulation of the screw retaining components by a user during the loading sequence. U.S. Pat. No. 6,155,145 discloses a similar approach in which a cam sleeve 400 is positioned by a user. Further, while a user would be loading a screw (“nail”) into the device, they may be required to oppose the force of a compression spring 610 for a significant travel distance. Since this spring is providing the retention force, it is likely stiff. Thus the loading sequence may pose challenges to a user who may need to concurrently steady the tool, exert significant thrust on a sharp fastener, and manually position cam sleeve 400.
U.S. Pat. No. 4,197,886 describes another device where a user may load a screw without touching or directly manipulating the components of the device, however while loading a fastener, the user is exerting force to position the retaining elements, namely retaining balls 94, their carrier sleeve 84 and a spring 88, which urges those elements forward, whereby the act of loading the fastener will temporarily store energy in spring 88 prior to reaching a triggering point where that energy is released and sleeve 84 is pushed forward, in turn causing balls 94 to be pushed radially inward through contact with cam surface 98. The effort exerted to position the screw retaining components of the device of this invention may limit productivity.
The screw retaining means of U.S. Pat. No. 4,197,886 and U.S. Pat. No. 5,996,452 are similar, however the diagrams of the later patent depict a flat head fastener with a tapered surface under the head. Since the taper angle is closer to the central axis of the tool than the inclined surface 104 which urges the retaining balls inward, the retaining force of that particular configuration may be directly related to the force exerted by the spring and therefore U.S. Pat. No. 5,996,452 was listed in the prior category. As the categories are defined in this background discussion, each could qualify for both categories depending on the screw head geometry which is selected.
U.S. Pat. No. 6,457,916 describes a prior art device of interest. This patent describes a device for receiving conventional tool shanks such as those conforming to ANSI B 107.4-1982. Thus this device is designed to receive a shank of length significantly greater than cross-sectional width which has a consistent geometrical outer profile aside from a circumferential detent groove to which significant thrust may be imparted between the device and said shank in both directions along the central axis of the device. Also of particular interest is the device described in this patent requires direct manipulation of an outer cam sleeve 14 during the unload cycle.
In operation, a user may directly manipulate outer cam sleeve 14 to a first position and release, subsequently allowing an appropriate tool bit 40 to be pushed into a bore 36 of device 10 where the device will cycle to a closed position without requiring direct manipulation of said sleeve 14 while the bit 40 is being loaded. While cycling between the unloaded and loaded configurations, sleeve 14 travels to a second position, whereby the geometry of that cam sleeve locks the installed bit 40 within the bore 36 of device 10 by means of a bit detent ball 16 protruding radially inward into bore 36 and a circumferential groove 44 in the shank of bit 40. To release the bit, a user directly manipulates cam sleeve 14 from its second position where the bit is held by bit ball 16 to its first position where bit 40 can be removed. The user may then release cam sleeve 14 and then directly grasp bit 40 to remove it from device 10. A subsequent bit 40 can then be loaded into device 10 without direct manipulation of the device while the bit is being loaded. The device described in this patent requires direct manipulation to position the cam sleeve 14 whenever a bit is to be unloaded and it contains no provisions to describe, suggest, or motivate any deviation from that style of operation nor does it illustrate or suggest any mechanics which would enable other operational procedures.